## Input a matrix into Abaqus (*MATRIX INPUT)

## Input a matrix into Abaqus (*MATRIX INPUT)

(OP)

Hi all,

This is what I'm currently attempting:

-Run a static analysis with contacts and centifugal nonlinear effects

-Use the resultant displacements and stresses in a new analysis so the contacts disappear completely (not enough with contact change).

I have tried loads of different methods to overcome the contact problem (restart, different dummy MPC arrangements, activating-deactivating contacts...), unfortunately none of them is good enough for what I seek and the best I could manage was a new analysis without the centrifugal nonlinear effect taken into account, which is not ideal as the stiffening effect of the centrifugal load is considerable.

Recently, I came up with the following approach:

-Run the nonlinear static contact analysis generating mass and stiffness matrices (*MATRIX OUTPUT...)

-Use deformed mesh and stress initial conditions from .odb in a second analysis. In this second analysis I'm also trying to use the stiffness and mass matrices obtained in the first analysis as an input.

Reading the Abaqus documentation it seems like importing the mass and stiffness matrices from the first analysis would be possible by using *MATRIX INPUT and *MATRIX ASSEMBLE. However, when I go down this line I get the following error: ***ERROR: NO STEP DEFINITION WAS FOUND . This makes very little sense to me as I have obviously defined a Step in my analysis... I have no experience whatsoever using this command so I was wondering if somebody could give me a hand on this, as I could not find any examples on the internet.

Thanks in advance,

Gramsey

This is what I'm currently attempting:

-Run a static analysis with contacts and centifugal nonlinear effects

-Use the resultant displacements and stresses in a new analysis so the contacts disappear completely (not enough with contact change).

I have tried loads of different methods to overcome the contact problem (restart, different dummy MPC arrangements, activating-deactivating contacts...), unfortunately none of them is good enough for what I seek and the best I could manage was a new analysis without the centrifugal nonlinear effect taken into account, which is not ideal as the stiffening effect of the centrifugal load is considerable.

Recently, I came up with the following approach:

-Run the nonlinear static contact analysis generating mass and stiffness matrices (*MATRIX OUTPUT...)

-Use deformed mesh and stress initial conditions from .odb in a second analysis. In this second analysis I'm also trying to use the stiffness and mass matrices obtained in the first analysis as an input.

Reading the Abaqus documentation it seems like importing the mass and stiffness matrices from the first analysis would be possible by using *MATRIX INPUT and *MATRIX ASSEMBLE. However, when I go down this line I get the following error: ***ERROR: NO STEP DEFINITION WAS FOUND . This makes very little sense to me as I have obviously defined a Step in my analysis... I have no experience whatsoever using this command so I was wondering if somebody could give me a hand on this, as I could not find any examples on the internet.

Thanks in advance,

Gramsey

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

Thanks for your response. I actually thought the same and tried without part and assembly definition. In fact, I have taken that template that you mention as example but still not working for me

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

I still haven't managed to make this work. I just want to successfully use the *MATRIX INPUT command. So I've got the .sim file from a previous analysis (same model I attached last time). However, the following error comes up:

***ERROR: SIM database file is not a valid SIM file:

/folder/example/job_matrix_trial_X4.sim

I have used the *MATRIX INPUT command as follows:

*MATRIX INPUT, NAME=MAT1, INPUT=job_matrix_trial_X4.sim, MATRIX=STIFFNESS

Something I'm missing/doing wrong? Why is the SIM file not valid? It comes from a successfully run analysis...

Thanks in advance

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

S T E P 4 M A T R I X G E N E R A T E

THE FOLLOWING GLOBAL MATRICES WILL BE GENERATED AND WRITTEN TO job_matrix_trial_X4.sim

STIFFNESS

MASS

Regarding generating a text output, I have generated mass and stiffness .mtx too. Is there any way to use them in with *MATRIX INPUT?

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

## RE: Input a matrix into Abaqus (*MATRIX INPUT)

Aside from that drawback, I'm trying to include a stress initial condition based on the previous .odb. It comes with this error:

***ERROR: OdbError: Cannot open file

/tmp/u5003396-2019.09.20-09.51.32/job_matrix_trial.odb. ***ERROR:

"/tmp/u5003396-2019.09.20-09.51.32/job_matrix_trial.odb" is not an

Abaqus database file.

Note that the stress initial condition works perfectly fine without *MATRIX INPUT as results look fine with no errors. However, when both are active in the .inp the above error appears. Any idea why this happens?

Thanks in advance,

Gramsey

## RE: Input a matrix into Abaqus (*MATRIX INPUT)